JPH09171889A - Heating device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heating device having high performances free from fixing failure, uneven brightness, and offset which has a low power consumption, and can be shortened in wait time, enhanced in durability by the prevention of temperature rise in a non-paper passing part, and used as a fixing device in a full color image forming device. SOLUTION: This device has magnetic flux generating means 4, 5, and an induction heating element 6 electromagnetically induction heated by the action of the magnetic fluxes generated from the magnetic flux generating means 4, 5. A matter P to be heated is introduced to a heating part N, and carried in contact to the induction heating element 6 directly or through a heat transfer member, and the matter P is heated by the heat of the induction heating element 6. This device also has a magnetic flux regulating means 7 for changing the density distribution related to the heating part longitudinal direction crossing the carrying direction of the matter to be heated of the magnetic fluxes acting on the induction heating element 6 from the magnetic flux generating means 4, 5 in the heating part N.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic induction heating type heating device and an image forming apparatus provided with the heating device as an image heating device for image fixing and the like.

[0002]

2. Description of the Related Art For the sake of convenience, an image heating and fixing device in an image forming apparatus such as an electrophotographic copying machine, a printer and a fax machine will be described as an example.

An image heating and fixing device in an image forming apparatus uses a toner made of heat-meltable resin or the like by an appropriate image forming process means such as electrophotography, electrostatic recording, magnetic recording, etc. in an image forming portion of the image forming apparatus. It is an apparatus that heats and fixes an unfixed toner image formed on a surface of a recording material by a direct method or an indirect (transfer) method using a developer as a permanently fixed image.

Conventionally, as such an image heating and fixing device, there are various devices such as a heat roller system, a film heating system, and an electromagnetic induction heating system.

A. Heat roller type This is composed of a rotating roller pair of a fixing roller (heat roller) and a pressure roller, which have a heat source such as a halogen lamp built therein and are heated and adjusted to a predetermined fixing temperature, and a pressure contact nip portion of the roller pair. This is a device that heats and fixes an unfixed toner image on the surface of a recording material by introducing a recording material on which an unfixed toner image is formed and carried as a material to be heated into a (fixing nip portion) and nipping and conveying the recording material.

However, this apparatus has the problems that the heat capacity of the fixing roller is large, the power required for heating is large, and the wait time (wait time from power-on of the apparatus to the state in which print output is possible) is long. .

In the case of a fixing device for a full-color image forming apparatus, since the ability to heat and melt a maximum of four toner layers is required, the fixing roller has its cored bar having a high heat capacity, and the fixing roller has a high heat capacity. A rubber elastic layer is provided on the outer periphery of the core metal in order to wrap the layer and uniformly melt the layer, and the toner image is heated through the rubber elastic layer. As described above, in the case of an apparatus using a fixing roller having a particularly large heat capacity, there is a delay between the temperature control of the fixing roller and the temperature rise of the roller surface, which causes problems such as fixing failure, uneven gloss, and offset. Was there.

B. Film heating method This has a heating body and a film in which one surface slides on this heating body and the other surface moves in contact with the recording material, and the heat of the heating body is applied to the recording material via the film. Then, it is an apparatus for heating and fixing the unfixed toner image on the surface of the recording material (JP-A-63-313182, JP-A-2-157878).
Japanese Patent Laid-Open No. 4-44075 to 44083, 2049.
No. 80-204984, etc.).

In such a film heating type apparatus, a low-heat capacity ceramic heater or the like can be used as a heating body, and a heat-resistant and thin low-heat capacity one can be used as a film, and a heat roller using a fixing roller having a large heat capacity. Compared to the device of the system, it has the advantages that power consumption and wait time can be remarkably reduced, the quick start property is provided, and the temperature rise inside the machine can be suppressed.

C. Electromagnetic induction heating method This uses an electromagnetic induction heating element as a heating element, and a magnetic field is applied to the electromagnetic induction heating element by a magnetic field generating means to be heated by Joule heat generation based on an eddy current generated in the electromagnetic induction heating element. This is an apparatus for applying heat to a recording material as a material to heat and fix an unfixed toner image on the surface of the recording material.

Japanese Patent Publication No. 5-9027 discloses a heat roller type apparatus for electromagnetically heating a fixing roller made of a ferromagnetic material. The heat generation position can be brought close to the fixing nip portion, and a halogen lamp is used. It achieves a more efficient fixing process than the heat roller type device used as a heat source.

However, since the heat capacity of the fixing roller is large, there is a problem that a large amount of electric power is required to raise the temperature of the fixing nip portion with a limited electric power.

Japanese Unexamined Patent Publication No. 4-166966 discloses an electromagnetic induction heating type fixing device using a film-shaped fixing roller having a reduced heat capacity.

However, in a film-shaped fixing roller having a reduced heat capacity, the heat flow in the lengthwise direction (longitudinal direction of the fixing nip portion) is obstructed. There has been a problem that excessive temperature rise (temperature rise in the non-sheet passing portion) occurs and the life of the film and the pressure roller is shortened. The problem of the temperature rise in the non-sheet passing portion is the same as in the case of the film heating type device of the item b.

[0015]

Therefore, the image heating and fixing device of the image forming apparatus has low power consumption.
The wait time can be shortened, excessive temperature rise can be prevented in the non-sheet passing area, and high durability can be achieved. It can be used as a fixing device in a full-color image forming apparatus. There is a demand for a heating device having high performance such as high performance that does not occur.

The present invention provides an electromagnetic heating type heating device and a device using the heating device which can meet such a demand.

[0017]

The present invention is a heating device and an image forming apparatus characterized by the following configurations.

(1) It has a magnetic flux generating means and an induction heating element for generating electromagnetic induction heat by the action of the magnetic flux generated by the magnetic flux generating means, and a material to be heated is introduced into the heating portion to directly or to the induction heating element. A heating device of an electromagnetic induction heating system that heats a material to be heated by the heat generated by an induction heating element in contact with a heating material and conveys the material to be heated by the magnetic flux acting on the induction heating element from the magnetic flux generating means in the heating section. A heating device having a magnetic flux adjusting means for changing the density distribution in the longitudinal direction of the heating portion intersecting the transporting direction of.

(2) The heating device according to (1), wherein the induction heating element is a rotating body.

(3) The heating device according to (2), wherein the rotation induction heating element is a seamless film having a small heat capacity.

(4) Any one of (1) to (3), wherein the heating section has a rotary pressurizing member which comes into contact with the induction heating element directly or through the heat transfer material to form a nipping and conveying nip portion for heating the material. The heating device according to one.

(5) The magnetic flux adjusting means corresponds to a non-sheet passing area portion of the heating portion when a heated material having a size smaller than the maximum heated material that can be used for passing paper through the apparatus is passed. The heating device according to any one of (1) to (4), characterized in that the acting magnetic flux density for the induction heating element portion is made weaker than the acting magnetic flux density for the induction heating element portion corresponding to the paper sheet area portion.

(6) The heating device according to any one of (1) to (5), characterized in that the magnetic flux adjusting means functions according to the size of the material to be heated that is used for passing the paper through the device. .

(7) The heating device according to any one of (1) to (6), wherein the magnetic flux adjusting means is a movable magnetic flux shielding member.

(8) The heating device according to any one of (1) to (6), wherein the magnetic flux adjusting means is a magnetic member that is inserted into and removed from the magnetic flux generating means.

(9) The magnetic flux adjusting means is a magnetic flux damping coil attached to the magnetic flux generating means (1)
The heating device according to any one of (1) to (6).

(10) The magnetic flux adjusting means is a magnetic flux attenuating coil attached to the magnetic flux generating means, and corresponds to the attenuating coil of the magnetic flux generating means by consuming the induced current generated in the attenuating coil in the load circuit. Any one of (1) to (6), characterized in that the magnetic flux density generated in a portion is weakened.
The heating device according to any one of the above.

(11) The material to be heated is a recording material carrying an image, and is an image heating apparatus for heating the image, according to any one of (1) to (10). Heating device.

(12) The heating device according to (11), which is an image heating and fixing device for heating and fixing the image on the recording material as a permanent image.

(13) An image forming apparatus comprising the image heating device described in (11) or the image heating fixing device described in (12).

<Operation> By the magnetic flux adjusting means, it corresponds to the non-sheet passing area portion of the heating portion when the heated material of a size smaller than the maximum size of the heated material that can be passed through the apparatus is passed. By changing the magnetic flux density acting on the induction heating element part so that it is weaker than the acting magnetic flux density on the induction heating element part corresponding to the paper-passing area part, an excessive temperature rise in the non-paper-passing part (temperature rise in the non-paper-passing part ) Can be prevented or alleviated, and the durability of the device can be increased.

By using an induction heating body or a member including the induction heating body and a heat transfer material having a small heat capacity, the heating section can be quickly started up to a predetermined temperature with low power consumption, and the wait time can be shortened. It is possible to provide high performance and quick start.

It is possible to configure a heating device that can be used as a fixing device in a full-color image forming apparatus and that has high performance without causing defective fixing, uneven gloss, and offset.

[0034]

BEST MODE FOR CARRYING OUT THE INVENTION

<Embodiment 1> (FIGS. 1 to 6) (1) Example of Image Forming Apparatus FIG. 1 is a schematic configuration diagram of an example of an image forming apparatus. The image forming apparatus of this example is a four-color electrophotographic color printer.

Reference numeral 11 denotes an electrophotographic photosensitive drum (image bearing member) made of an organic photosensitive member, which is rotationally driven in a clockwise direction indicated by an arrow at a predetermined process speed (peripheral speed).

The photosensitive drum 11 is uniformly charged with a predetermined polarity and potential by a charging device 12 such as a charging roller during its rotation process.

Next, by the laser light L output from the laser optical box (laser scanner) 13 on the charging surface,
The scanning exposure processing of the target image information is performed. The laser optical box 13 outputs a laser beam L modulated (on / off) in response to a time-series electric digital pixel signal of the target image information from an image signal generator such as an image reading device (not shown) and outputs the laser light L. Is subjected to scanning exposure, and an electrostatic latent image corresponding to the target image information subjected to scanning exposure is formed on the surface of the rotary photosensitive drum 11 by this scanning exposure. 13a is a laser optical box 13
Is a mirror that deflects the output laser beam from the device to the exposure position of the photoconductor drum 11.

In the case of forming a full-color image, the first color separation component image of the target full-color image, for example, the yellow component image is subjected to scanning exposure / latent image formation, and the latent image is included in the four-color developing device 14. Yellow developing device 1
By the operation of 4Y, it is developed as a yellow toner image. The yellow toner image is a primary transfer portion T1 which is a contact portion (or a proximity portion) between the photosensitive drum 11 and the intermediate transfer drum 16.
Is transferred onto the surface of the intermediate transfer drum 16. After the toner image is transferred onto the surface of the intermediate transfer body drum 16, the surface of the rotating photosensitive drum 11 is cleaned by a cleaner 17 after removing adhering residues such as transfer residual toner.

The process cycle of charging, scanning exposure, development, primary transfer, and cleaning as described above is the second (for example, the magenta component image, the magenta developing unit 14M operates) and the third (for example, cyan) of the target full-color image. Component image, cyan developing device 14C is activated), and fourth (for example, black component image, black developing device 14BK is activated) color separation component images are sequentially executed, and a yellow toner image / magenta toner is formed on the surface of the intermediate transfer body drum 16. The toner images of four colors, that is, the image, the cyan toner image, and the black toner image, are sequentially superimposed and transferred, and a color image corresponding to the target full-color image is composited and formed.

The intermediate transfer drum 16 has an elastic layer having a medium resistance and a surface layer having a high resistance on a metal drum. The intermediate transfer drum 16 is in contact with or close to the photosensitive drum 11 and has substantially the same circumference as the photosensitive drum 11. It is rotationally driven in the counterclockwise direction indicated by an arrow at a speed to apply a bias potential to the metal drum to transfer the toner image on the side of the photoconductor drum 11 to the surface side of the intermediate transfer body drum by the potential difference from the photoconductor drum 11.

The color toner image synthetically formed on the surface of the rotary intermediate transfer drum 16 is subjected to the secondary transfer at the secondary transfer portion T2 which is a contact nip portion between the rotary intermediate transfer drum 16 and the transfer roller 15. The image is transferred onto the surface of the recording material P, which is fed to the transfer portion T2 from a paper feeding portion (not shown) at a predetermined timing. The transfer roller 15 supplies an electric charge having a polarity opposite to that of the toner from the back surface of the recording material P to sequentially transfer the composite color toner image from the surface of the intermediate transfer drum 16 side to the recording material P side in a batch.

The recording material P that has passed through the secondary transfer portion T2 is separated from the surface of the intermediate transfer body drum 16 and is introduced into the image heating and fixing device 10, where it is subjected to the heat fixing process of the unfixed toner image to form a color image formed product. Is discharged to a paper discharge tray (not shown) outside the machine.

The image heating and fixing device 10 is an electromagnetic induction heating type device according to the present invention. The fixing device 10 will be described in detail in the next section (2).

After the transfer of the color toner image onto the recording material P, the rotary intermediate transfer member drum 16 is cleaned by the cleaner 18 after removing the transfer residual toner, adhering residues such as paper dust. The cleaner 18 is normally held in a non-contact state with the intermediate transfer body drum 16, and is in a contact state with the intermediate transfer body drum 16 during the secondary transfer execution of the color toner image from the intermediate transfer body drum 16 to the recording material P. Retained.

The transfer roller 15 is also held in a non-contact state with the intermediate transfer body drum 16 at all times, and during the secondary transfer execution of the color toner image from the intermediate transfer body drum 16 onto the recording material P, the intermediate transfer body drum 16 is carried out. Recording material P
Is held in contact via the.

(2) Image heating and fixing device 10 FIGS. 2 and 3 are side cutaway model views of the image heating and fixing device 10, FIG. 4 is a vertical front view model view of the heating assembly, and FIG. 5 is a cutout of the heating assembly. It is a perspective view.

The fixing device 10 includes a heating assembly 1
And the pressure roller 2 as a rotary pressure member.

The heating assembly 1 has a cylindrical film guide member 3, an exciting coil 4 as a magnetic flux generating means arranged in its inner space, a magnetic core (high transmittance core) 5, and a cylindrical film guide member 3 loosened. A cylindrical (seamless) fixing film 6 as an induction heating element, which is fitted onto the outer peripheral surface of the cylindrical film guide member 3, is arranged so as to be slidable in the vertical direction a and b along the inner circumference of one end side of the cylindrical film guide member 3. It is composed of a pair of left and right arc-shaped magnetic flux shielding plates 7 and the like as magnetic flux adjusting means.

The pressure roller 2 is an elastic roller comprising a cored bar 2a and a 2 mm thick silicone rubber layer 2b covering the outer periphery of the cored bar.

The heating assembly 1 and the pressure roller 2 are vertically pressed into contact with each other and assembled in an apparatus casing (not shown) to form a fixing nip portion (heating nip portion) N having a predetermined width therebetween. In the fixing nip portion N, the inner surface of the fixing film 1 is in close contact with the lower surface of the cylindrical film guide member 3.

The pressure roller 2 is rotationally driven in the clockwise direction shown by the arrow in FIG.
The rotational force acts on the fixing film 5 by the frictional force in the fixing nip portion N between the roller 2 and the outer surface of the fixing film 6 due to the rotational driving of the fixing film 6, so that the fixing film 6 moves around the outer periphery of the cylindrical film guide member 3 and its inner surface. Rotates in a counterclockwise direction as indicated by an arrow while closely sliding on the lower surface of the cylindrical film guide member 3 in the fixing nip portion N.

The exciting coil 4 generates an alternating magnetic flux by the alternating current supplied from the exciting circuit 40 (FIG. 5), the alternating magnetic flux is guided to the magnetic core 5 and acts on the fixing nip portion N, and at the fixing nip portion N. An eddy current is generated in the electromagnetic induction heating layer of the fixing film 6 described later. The eddy current generates Joule heat due to the specific resistance of the electromagnetic induction heating layer. That is, by supplying an alternating current to the exciting coil 4, the fixing film 6 is brought into an electromagnetic induction heat generation state in the fixing nip portion N.

The temperature of the fixing nip portion N is controlled to a predetermined fixing temperature by controlling the alternating current supplied from the exciting circuit 30 to the exciting coil 4 by the temperature adjusting system 100 including a temperature detecting means (not shown). It

Thus, the fixing film 6 is rotated by the rotation of the pressure roller 2, and the alternating current is supplied from the exciting circuit 40 to the exciting coil 4, so that the temperature of the fixing nip portion N rises to a predetermined temperature. In the fixed state, between the rotary fixing film 6 and the pressure roller 2 in the fixing nip portion N,
By introducing the recording material P that carries the unfixed toner image t as a material to be heated, the recording material P comes into close contact with the outer surface of the fixing film 6 and the fixing nip portion N together with the fixing film 6.
In the course of passing through the fixing nip portion, the recording material P and the unfixed toner image t are heated by the heat generation of the fixing film 6 which is electromagnetically heated, and the toner image is heated and fixed.
The recording material P passing through the fixing nip portion N is separated from the outer surface of the fixing film 6 at the exit side of the fixing nip portion N and conveyed.

A. In the heating assembly 1, the cylindrical film guide member 3 has an insulating property that does not prevent passage of magnetic flux.
It is a heat-resistant member that supports the exciting coil 4 and the magnetic core 5 and guides the inner surface of the cylindrical fixing film 6 rotating outside the member 2 to ensure the stability of rotation of the fixing film 6. To do.

B. The exciting coil 4 of this example is formed by using an insulation-coated electric wire and winding it into a horizontally long boat shape whose outer shape substantially corresponds to the inner surface of the cylindrical film guide member 3.
The cylindrical film guide member 3 is inserted and arranged in the cylindrical film guide member 3 by receiving the outer surface of the lower surface of the inner surface of the cylindrical film guide member 3. The exciting coil 4 must generate sufficient alternating magnetic flux for heating, but for that purpose it is necessary to have a low resistance component and a high inductance component. In this example, a high-frequency φ1 insulating covered electric wire in which thin wires are bundled as a core wire is wound around the fixing nip portion N 12 times to form the exciting coil 4. An exciting circuit 30 is connected to the exciting coil 4, and the exciting circuit 40 can supply an alternating current of 50 KHz to the exciting coil 4.

C. The magnetic core 5 is a horizontally long ferrite core, and is located substantially at the center of the horizontally long boat-shaped exciting coil 4 and supported by the cylindrical film guide member 3.
The magnetic core 5 serves to efficiently enhance the alternating magnetic flux generated by the exciting coil 4 in the fixing nip portion N.

D. The fixing film 6 is a cylindrical member including an electromagnetic induction heating layer, has an inner diameter slightly larger than the outer diameter of the cylindrical film guide member 3, and fits loosely on the cylindrical film guide member 3.

FIG. 6A is a schematic diagram of the layer structure of the fixing film 6. The fixing film 6 of this example includes an electromagnetic induction heating layer 6a on the inner side (the film guide member 3 side), an elastic layer 6b on the outer side thereof, and a release layer (surface layer; pressure roller 2 side) 6c on the outer side thereof. It is a composite layer structure of three layers. The heat of the electromagnetic induction heating layer 6a is transferred to the recording material P conveyed to the fixing nip portion N via the elastic layer 6b and the release layer 6c to heat the recording material P and the toner image t on the recording material P. .

The heat generating layer 6a is a material layer having an electromagnetic induction heat generating property that produces Joule heat by an eddy current due to the action of alternating magnetic flux, and is a metal or metal which is a good electric conductor of 10 ⁻⁵ to 10 ⁻¹⁰ Ω · cm such as nickel. Any compound or organic conductor may be used, and more preferably, pure metals such as iron and cobalt having high magnetic permeability and exhibiting ferromagnetism or compounds thereof can be used.

When the thickness of the heat generating layer 6a is thin, a sufficient magnetic path cannot be ensured and the magnetic flux may leak to the outside to reduce the heat generating energy of the heat generating layer itself. It tends to take a long time. Therefore, the thickness has an appropriate value depending on the values of the specific heat, the density, the magnetic permeability, and the resistivity of the material used for the heat generating layer 6a. In practice, a temperature rising rate of 3 ° C./sec or more can be obtained in the thickness range of 10 to 100 μm. did it.

The elastic layer 6b is a rubber layer such as silicone rubber. In this example, the elastic layer 6b is provided to improve the fixing of a color toner image composed of a maximum of four toner layers. It works by wrapping it in and melting it uniformly.

If the hardness of the elastic layer 6b is too high, the unevenness of the recording material or the toner layer cannot be followed and the image gloss unevenness occurs. Therefore, the hardness of the elastic layer 6b is 60.
(JIS-A) or less, preferably 45 ° or less.

The thermal conductivity λ of the elastic layer 6b is 6 × 1.
0 ^{−4 to} 2 × 10 ⁻³ [cal / cm · sec · deg.] Is preferable. When the thermal conductivity λ is smaller than 6 × 10 ⁻⁴ [cal / cm · sec · deg.], The thermal resistance is large and the temperature rising rate in the surface layer of the fixing film becomes slow.

The elastic layer 6b has a thickness of 100 to 300 μm.
If it is less than 100 μm, spot-like gloss unevenness is likely to occur when the ratio of a solid image is large as in a color image forming apparatus, and if it exceeds 300 μm, a thermal gradient between the surface and the heat generating layer 6a is generated. When the elastic layer is generated, thermal deterioration of the elastic layer is likely to occur.

The release layer 6c is for preventing toner from adhering to the surface of the fixing film, and has good releasability and heat resistance such as fluororesin such as PFA / PTFE / FEP, silicone resin, silicone rubber and fluororubber. The material can be selected.

The thickness is preferably 20 to 100 μm, and 20
If it is smaller than μm, there arises a problem that a part having poor releasability is formed due to coating unevenness and durability is insufficient.
On the other hand, if it exceeds 100 μm, a problem that heat conduction is deteriorated occurs, and especially in the case of a resin-based release layer, the hardness becomes too high, and the effect of the elastic layer 6b disappears.

The fixing film 6 used in this example comprises a heating layer 6a made of nickel and having a thickness of 50 μm, an elastic layer 6b made of silicone rubber and having a thickness of 200 μm, and a release layer 6c made of fluororesin and having a thickness of 30 μm. Layer is a composite layer film.

Further, as shown in FIG. 6B, the fixing film 6 may have a four-layer structure in which a heat insulating layer 6d is provided inside the heat generating layer 6a in the above-mentioned layer structure of the fixing film 6.
The heat insulating layer 6d is preferably a heat resistant resin such as a fluororesin, a polyimide resin, a polyamide resin, a polyamideimide resin, a PEEK resin, a PES resin, a PPS resin, a PFA resin, a PTFE resin, and a FEP resin. The thickness is 10 to 1
000 μm is preferred. When the thickness is smaller than 10 μm, the heat insulating effect cannot be obtained, and the durability is insufficient. 1
When it exceeds 000 μm, the distance from the magnetic core 5 to the heat generating layer 6a becomes large, and the magnetic flux does not reach the heat generating layer 6a sufficiently. When the heat insulating layer 6d is provided, the heating of the exciting coil 4 and the magnetic core 5 due to the heat generated in the heat generating layer 6a can be prevented, so that stable heating can be performed.

E. A pair of left and right arc-shaped magnetic flux shield plates 7 and 7 which are slidably arranged in the vertical direction a and b along the inner circumference of one end of the cylindrical film guide member 3 allow a small-sized recording material to pass therethrough. When paper is used, the action density of the alternating magnetic flux on the non-sheet passing area of the fixing nip portion N is made lower than the action density of the magnetic flux on the sheet passing area to prevent or reduce the temperature rise phenomenon of the non-sheet passing area. Play a role. As the magnetic flux shielding plates 7 and 7, non-magnetic and good electric conductors such as aluminum and copper are preferable.

In this embodiment, the recording material P is introduced into the fixing device 10 by one-side reference paper feeding. 4 and 5, O is a one-sided sheet passing reference line, A is a sheet passing area portion of a large size recording material (the maximum size recording material that can be passed through the apparatus), and B is a sheet passing area portion of a small size recording material. , C are non-sheet passing area portions (AB) when a small-sized recording material is used.

The pair of left and right arc-shaped magnetic flux shielding plates 7 and 7
Is the non-sheet passing area portion C of the cylindrical film guide member 3.
Circumferential guide groove 3a provided on the inner surface of the end on the side where the
Are slidable in the vertical directions a and b along the circumferential guide groove portions 3a on the left and right sides of the magnetic core 5, and have a width corresponding to the width of the non-sheet passing area portion C.

By slidably moving downward b, the state (closed position) is inserted between the left and right outer surfaces of the exciting coil 4 and the inner surface of the cylindrical film guide member 3 as shown in FIG.

Further, as each of them is slid upwardly, as shown in FIG. 3, it is in a state (open position) where it comes out from between the left and right outer surfaces of the exciting coil 4 and the inner surface of the cylindrical film guide member 3.

[0075] When the magnetic flux shielding plates 7 and 7 are in the closed position in FIG. 2, the non-sheet passing area portion C is excited when the small size recording material is passed in the longitudinal direction (longitudinal direction) of the fixing nip portion N. The alternating magnetic flux from the coil 4 is blocked or reduced with the fixing film 6 by the closed magnetic flux shielding plates 7 and 7, and the action density of the magnetic flux acts on the small-size sheet passing region B of the fixing nip portion N. Lower than density. As a result, the fixing film portion corresponding to the small-size sheet passing area portion B in the fixing nip portion has a substantially uniform predetermined electromagnetic induction heat generation to have an optimum temperature distribution for fixing, but corresponds to the non-sheet passing area portion C. The electromagnetic induction heat generation of the fixing film portion is lower than that, so that the temperature rising phenomenon of the non-sheet passing portion is prevented or alleviated.

. When the magnetic flux shield plates 7 and 7 are in the open position in FIG. 3, the magnetic flux shield plates 7 and 7 do not shield the magnetic flux, and the alternating magnetic flux generated in the exciting coil 4 is a large size sheet passing area in the fixing nip portion. It acts at a predetermined high density over the entire area of the portion A, and the entire area of the fixing film portion corresponding to the large-size sheet passing area portion A in the fixing nip portion has a substantially uniform predetermined electromagnetic induction heat generation and has a temperature distribution optimum for fixing. Become.

The magnetic flux shielding plates 7 and 7 are arm portions 7a, respectively.
The drive means 70 (connected to FIG. 4 via 7a,
The switching movement between the closed position and the open position is automatically performed by the control circuit 101 and the driving means 70 according to the size of the recording material that is used for passing the paper through the apparatus. Although a concrete structural example of the drive means 70 for opening and closing the magnetic flux shielding plates 7 and 7 is omitted in the drawing, it is appropriately and easily provided by a drive source such as a motor or solenoid and a motion mechanism such as a lever, link, cam or belt. Can be designed and configured as

The control circuit 101 switches the magnetic flux shield plates 7 to the closed position shown in FIG. 2 when the recognition means (not shown) detects that the recording material P to be used as paper is small in size. The drive means 70 is controlled to move. By switching the magnetic flux shield plates 7 to the closed position, the temperature rise phenomenon of the non-sheet passing portion is prevented or alleviated as described above.

Further, the control circuit 101 switches the magnetic flux shield plates 7 to the open position shown in FIG. 3 when the recognition means detects that the recording material P used for passing the paper through the apparatus has a large size. The driving means 70 is controlled as described above. As a result, as described above, the magnetic flux reaching the fixing film in the longitudinal direction of the fixing nip portion is not disturbed and heat is generated over the entire area, and the temperature distribution is optimal for fixing a large-sized recording material.

The image forming apparatus of the above (1) has a feature that it can deal with various recording materials by adopting the intermediate transfer body drum 16. The configuration of the image heating and fixing device 10 of the present embodiment described above, in dealing with such a recording material, reduces unevenness in the temperature distribution of the fixing film 6 due to the difference in paper size as compared with the conventional case, and fixes with high throughput. Provide the ability.

In the image heating apparatus using the conventional fixing film, when the recording material of the small size is passed at the same throughput as the recording material of the large size, the temperature distribution unevenness of up to 60 degrees occurs. In this example, since the uneven temperature distribution is suppressed to a low level, high full throughput can be maintained.

In this example, the example of one-sided standard paper feeding in which the recording material is passed toward one side in the lengthwise direction is shown, but also in the apparatus of central reference paper feeding, the magnetic flux shielding plate 7 is not passed on both sides. The same effect can be obtained by disposing it in the area.

Although the four-color image forming apparatus has been described in this embodiment, it may be applied to a monochrome or one-pulse multi-color image forming apparatus. In this case, the elastic layer 6b can be omitted in the fixing film 6.

<Embodiment 2> (FIGS. 7 to 9) FIG. 7 is a partially cutaway side view model of the image heating and fixing device 10 of Embodiment 2 of the present invention, and FIG. 8 is a cutaway perspective view of the heating assembly. FIG. 9 is a schematic diagram of the layer structure of the fixing film.

In the fixing device 10 of this embodiment, the heating assembly 1 has a cylindrical film guide member 3 and a thickness of 0 as an induction heating element fixedly arranged on the inner bottom surface of the film guide member 3 along its length. Elongated sheet metal of 7 mm 8
And as a magnetic flux generating means arranged on the sheet metal 8,
A U-shaped magnetic core (ferrite core) 5 having a downward cross section, an exciting coil 4 wound around the core 5, and an insertion as a magnetic flux adjusting means that is movable back and forth in the U-shaped magnetic core 5 at one end side of the magnetic core 5. It comprises a core 5A and a cylindrical (seamless) fixing film 6A as a heat transfer member, which is loosely fitted onto the cylindrical film guide member 3 and the like.

The fixing film 6A in the apparatus of this embodiment is not provided with the electromagnetic induction heat generating property, and as shown in a layer structure model diagram in FIG. 9, a cylindrical base film 6e and an elastic layer laminated on the outer peripheral surface thereof. 6b and a release layer 6c further laminated on the outer peripheral surface thereof. This example has a thickness of 5
A 0 μm seamless polyimide sleeve was used as a base film 6e, silicone rubber was laminated on the outer peripheral surface of the elastic film 6b to a thickness of 200 μm, and the outer peripheral surface of the release film 6c was coated with a fluororesin of about 20 μm. The inner diameter is slightly larger than the outer diameter of the cylindrical film guide member 3, and the cylindrical film guide member 3 is loosely fitted onto the cylindrical film guide member 3.

In the apparatus of this embodiment, the cylindrical fixing film 6A is rotated around the cylindrical film guide member 3 by the rotational driving of the pressure roller 2 as in the apparatus shown in FIGS.

An alternating magnetic flux generated by supplying an alternating current to the exciting coil 4 from the exciting circuit 40 causes the fixed elongated sheet metal 8 as an electromagnetic induction heating element to generate heat by electromagnetic induction, and the heat generated fixes the fixing nip portion N. The film 6A is heated, and the recording material P conveyed to the fixing nip portion N and the toner image t on the recording material are heated.

In the fixing nip portion N, the fixing film 6A may be heated by directly sliding the inner surface of the fixing film 6A in close contact with the lower surface of the fixed elongated metal plate 8 serving as an electromagnetic induction heating element.

In the apparatus configuration of this embodiment, since the fixed type heating element 8 is used, an inexpensive resin sleeve which does not include an electromagnetic induction heating layer as the fixing film 6A and has little thermal deterioration can be used.

The insert core 5A is a member of high magnetic permeability, and may be made of the same material as the magnetic core 5 (ferrite core) of the exciting coil 4.

The insertion core 5A is inserted into the U-shaped magnetic core 5 at one end side of the magnetic core 5 (the side where the non-paper passing area portion C is generated) by the driving means 50 in accordance with the size of the recording material used for paper passing. It is moved back and forth c ・ d. Although a concrete structural example of the driving means 50 is omitted in the drawing, it is appropriately and easily designed and configured by a driving source such as a motor or a solenoid and a motion mechanism utilizing a lever, a link, a cam, a belt, a rack, a pinion or the like. can do.

The driving means 50 controls the amount of advance / retreat of the insertion core 5A by a control circuit (not shown) according to the size of the recording material used for paper passing.

[0094] When a small-sized recording material is used for sheet passing, the insertion core 5A is moved in the insertion direction c into the U-shaped magnetic core 5 up to a portion corresponding to the non-sheet passing area portion C.

As a result, in the longitudinal direction of the fixing nip portion N, the alternating magnetic flux from the exciting coil 4 with respect to the non-sheet passing area portion C when the small size recording material is passed through is the insertion core 5A.
It is possible to reduce the amount of heat generated by passing through the inside and reducing the magnetic flux passing through the portion corresponding to the non-sheet passing area portion C of the fixed elongated sheet metal 8 as the electromagnetic induction heating element. As a result, the temperature distribution of the small-size sheet passing area portion B in the fixing nip portion is optimum for fixing, but the temperature of the non-sheet passing area portion C is lower than that, so that the temperature rise phenomenon of the non-sheet passing portion can be prevented. Is relaxed.

[0096] When a large-sized recording material is used, the insertion core 5A is moved from the inside of the U-shaped magnetic core 5 in the removal direction d so as to be located outside the large-sized paper passing area portion A.

As a result, the magnetic flux is not shielded by the insertion core 5A, and the fixed elongated sheet metal 8 as an electromagnetic induction heating element generates a large amount of electromagnetic induction heat in a substantially uniform manner over the entire area corresponding to the large-size sheet passing area portion A. The temperature distribution is optimal for fixing the size recording material.

Since this configuration can be controlled in a one-to-one correspondence with the width of the recording material size, the unevenness of the temperature distribution can be further reduced.

In this example, the example of the one-sided reference sheet passing in which the recording material is passed to one side in the lengthwise direction is shown, but also in the apparatus of the central reference sheet-passing, the insertion core 5A has the non-sheet passing area portion at both ends. The same effect can be obtained by arranging the above.

<Third Embodiment> (FIGS. 10 and 11) FIG. 10 is a partially cutaway side view model of the image heating and fixing device 10 of the third embodiment, and FIG. 11 is a structural model view of the magnetic field generating means. is there.

The apparatus of this example is different from the apparatus of FIGS. 2 to 5 in that the magnetic flux shielding plates 7 and 7 are not provided,
The difference is that the structure of the magnetic flux generating means is different, and the other structures are the same.

That is, the magnetic flux generating means in the apparatus of this embodiment is provided with the attenuation coil 206 at a portion corresponding to the non-sheet passing area C when the small size recording material is used. Damping coil 2
The terminal 06 is connected to a load circuit (not shown) via a switching element, and is set so that a load is applied in synchronization with a signal from the image forming apparatus.

The attenuating coil 206 consumes magnetic field energy in the load circuit at the time of passing a small size sheet, so that the fixing film portion corresponding to the small size sheet passing area portion B in the fixing nip portion generates a substantially uniform electromagnetic induction heat. Although the temperature distribution is optimum for fixing, the electromagnetic induction heat generation of the fixing film portion corresponding to the non-sheet passing area portion C is lower than that, so that the temperature rising phenomenon of the non-sheet passing portion is prevented or alleviated. It

In this example, the one-side reference paper feed is performed in which the recording material is passed to one side in the lengthwise direction. However, even in the central reference paper feed device, the damping coil 206 is provided at both ends of the non-paper feed area. The same effect can be obtained by arranging the above.

In addition, the above-described second embodiment (FIGS. 7 to 9).
With respect to the apparatus using the fixed type heating element 8, the attenuation coil 206 used in this configuration can be used instead of providing the magnetic field generation means 4 and 5 with the above-described insertion core 5A.
In this case, there is an advantage that an inexpensive fixing film 6A can be used.

Thus, according to the present embodiment, it is possible to prevent the excessive temperature rise of the non-sheet passing portion and perform the preferable heat treatment.
Especially in the configuration where the magnetic field energy is consumed in the load circuit,
It is not necessary to provide an exciting circuit separate from the magnetic field generating means (that is, the exciting circuit is only one of the magnetic field generating means in this example), and a simple structure can be obtained.

<Others> a) Like the image heating and fixing device of each of the above embodiments,
The cylindrical fixing film 6, 6A is attached to the film guide member 3
By loosely fitting the roller to the outside and rotating the pressure roller on which the fixing nip portion N is formed (pressure roller drive system)
The device configuration for rotating the fixing films 6 and 6A is such that no tension is applied to the film portion other than the fixing nip portion and its vicinity when the fixing film is rotated (tensionless).
The shift force of the film along the length of the film guide member is small when the fixing film rotates. Therefore, although the means for restricting the deviation of the film is omitted in the drawing, there is an advantage that a simple means such as a simple flange member for receiving the end portion of the film may be used.

B) The fixing films 6 and 6A may have an apparatus structure in which an endless belt-like member is suspended and stretched between two or more members and rotationally driven by a pressure roller or a driving means other than the pressure roller. Alternatively, an apparatus configuration may be adopted in which the end-fixed long fixing film 6 or 6A wound in a roll is moved.

C) It is also possible to adopt a device configuration in which the material to be heated is brought into direct contact with the fixedly arranged electromagnetic induction heating element 8 to perform heat treatment.

D) The heating device of the present invention is not limited to the image heating and fixing device of each embodiment, but a heating device for heating a recording material carrying an image to modify surface properties such as gloss, and assumed heating. It can be widely used as a means and device for heat-treating a material to be heated, such as an image heating device such as a device, a heating and drying device for a material to be heated, a heating laminating device, and the like.

[0111]

As described above, according to the present invention, the electromagnetic induction heating type heating device has low power consumption.
The wait time can be shortened, excessive temperature rise can be prevented in the non-sheet passing area, and high durability can be achieved. It can be used as a fixing device in a full-color image forming apparatus. No defective fixing, uneven gloss, or offset occurs. It is possible to obtain a heating device having high performance, such as high performance.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an example of an image forming apparatus according to a first embodiment.

FIG. 2 is a partial cutaway side view of the image heating and fixing device (when the magnetic flux shielding plate is closed).

FIG. 3 is a partially cutaway side view of the image heating and fixing device (when the magnetic flux shield plate is open).

FIG. 4 is a vertical sectional front view of the heating assembly.

FIG. 5 is a cutaway perspective view of the heating assembly.

6 (a) and 6 (b) are schematic diagrams of a layer structure of a fixing film (induction heating element film).

FIG. 7 is a partially cutaway side view of a heating assembly of the image heating and fixing device according to the second embodiment.

FIG. 8 is a cutaway perspective view of the heating assembly.

FIG. 9 is a schematic diagram of a layer structure of a fixing film

FIG. 10 is a partially cutaway side view of a heating assembly of the image heating and fixing device according to the third embodiment.

FIG. 11 is a structural model diagram of magnetic field generating means.

[Explanation of symbols]

 10 Heat Fixing Device 1 Heating Assembly 2 Pressure Roller 3 Cylindrical Film Guide Member 4 Excitation Coil 5 Magnetic Core 6.6A Fixing Film 7 Magnetic Flux Shielding Plate 8 Insertion Core

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroki Kisu 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc.

Claims (13)

[Claims] 1. A magnetic flux generating means, and an induction heating element for generating electromagnetic induction heat by the action of the magnetic flux generated by the magnetic flux generating means,
A heating device of an electromagnetic induction heating system, which introduces a material to be heated into a heating portion and conveys it to the induction heating element directly or in contact via a heat transfer material to convey the material to be heated by the heat generated by the induction heating element, A heating device comprising a magnetic flux adjusting means for changing the density distribution of the magnetic flux acting on the induction heating element from the magnetic flux generating means in the heating part in the longitudinal direction of the heating part intersecting the conveying direction of the material to be heated. 2. The heating device according to claim 1, wherein the induction heating element is a rotating body. 3. The heating device according to claim 2, wherein the rotation induction heating element is made of a seamless film having a small heat capacity. 4. The rotating pressurizing member forming a nipping and nip part for sandwiching a material to be heated by contacting an induction heating element directly or via a heat transfer material in the heating part. The heating device described. 5. The magnetic flux adjusting means corresponds to a non-sheet passing area portion of a heating unit when a heated material having a size smaller than a maximum heated material that can be used for passing paper through the apparatus is passed. 5. The heating device according to claim 1, wherein the acting magnetic flux density for the heating element portion is made weaker than the acting magnetic flux density for the induction heating element portion corresponding to the paper sheet area portion. 6. The heating device according to claim 1, wherein the magnetic flux adjusting means functions in accordance with a size of a material to be heated which is used as a sheet to be passed through the device. 7. The heating device according to claim 1, wherein the magnetic flux adjusting means is a movable magnetic flux shielding member. 8. The heating device according to claim 1, wherein the magnetic flux adjusting means is a magnetic member that is inserted into and removed from the magnetic flux generating means. 9. The heating device according to claim 1, wherein the magnetic flux adjusting means is a magnetic flux attenuation coil attached to the magnetic flux generating means. 10. The magnetic flux adjusting means is a magnetic flux attenuating coil attached to the magnetic flux generating means, and a portion corresponding to the attenuating coil of the magnetic flux generating means by consuming an induced current generated in the attenuating coil in a load circuit. The heating device according to any one of claims 1 to 6, wherein the magnetic flux density generated in (1) is weakened. 11. The heating apparatus according to claim 1, wherein the material to be heated is a recording material carrying an image, and the image heating apparatus heats the image. . 12. The heating device according to claim 11, wherein the heating device is an image heating and fixing device that heats and fixes an image on a recording material as a permanent image. 13. An image forming apparatus comprising the image heating device according to claim 11 or the image heating and fixing device according to claim 12.